This invention relates to a photographic light sensitive material comprising a support bearing a silver halide emulsion layer thereon and particularly to a silver halide photographic light sensitive material capable of providing a high contrast.
A photographic plate-making process include a step of converting an original document having continuous tones into a halftone-dot image. In this step, an infectious development technique has been used as a technique capable of providing an image having a super-hard contrast.
A lithographic type silver halide photographic light sensitive material subject to an infectious development is comprised of, for example, a silver chlorobromide emulsion having an average grain size of 0.2 .mu.m, a relatively narrow grain size distribution, a uniform grain configuration and a relatively high silver chloride content (at least not less than 50 mol %). When processing the lithographic type silver halide photographic light sensitive material with an alkaline hydroquinone developer having a relatively low sulfite ion concentration, that is the so-called lithographic type developer, an image having a high contrast, a high sharpness and a high resolving power can be obtained.
However, the preservability of the above-mentioned lithographic type developers are deteriorated because this type of developers are liable to be air-oxidized. It is, therefore, very hard to keep the development quality in making repetition use of this type of developers.
On the other hand, there are known techniques for rapidly providing high contrast images without making use of any lithographic type developer mentioned above. In the techniques, a hydrazine derivative is contained in a silver halide photographic light sensitive material, as seen in Japanese Patent Publication Open to Public Inspection--hereinafter referred to as JP OPI Publication- No. 56-106244/1981, for example.
According to the above-mentioned techniques, a high-contrast image can be obtained by processing a light sensitive material with a developer excellent in preservability and capable of performing a rapid processing. In the techniques, however, a developer having a pH of not lower than pH 11.0 has been required for satisfactorily displaying the high-contrast rendering property of the hydrazine derivatives. In the high pH developers such as those having a pH of not lower than 11.0 mentioned above, the developing agents thereof are liable to be oxidized when the developers are exposed to the air, so that a ultrahigh contrast image may not be provided by the above-mentioned air-oxidation, though this type of developer is relatively stable as compared to the foregoing lithographic developers.
With the purpose of remedying the above-mentioned defects, JP OPI Publication No. 63-29751/1988 and European Patent No. 333,435 disclose the silver halide photographic light sensitive materials each containing a contrast-promoting agent capable of increasing the contrast of the light sensitive material even when making use of a relatively low-pH developer.
It has, however, been the present situation that, when processing a silver halide photographic light sensitive material containing such a contrast-promoting agent as mentioned above with a developer having a pH lower than 11.0, the contrast of the light sensitive material has been provided as yet not quite satisfactory, so that any satisfactory halftone dot quality has not been available.
In a silver halide photographic light sensitive material, a support such as those made of polyethylene terephthalate has commonly been used. However, such a support has a problem that an electrostatic charge is liable to generate particularly in the low humidity conditions such as in winter time.
If a light sensitive material is electrostatically charged, the discharge thereof produces the so-called static-marks or pin-holes produced by the adhesion of foreign matters such as dusts to the light sensitive material, so that the quality is seriously deteriorated and there may be some instances where the processing efficiency may be lowered because of remedying the quality deterioration. Therefore, the improvements of the above-mentioned problems have been strongly demanded.